This invention relates generally to the field of internal to combustion engines and, more particularly, to a flow guide component having improved tolerance to assembly and manufacturing variations.
Combustion engines are machines that convert chemical energy stored in fuel into mechanical energy useful for generating electricity, producing thrust, or otherwise doing work. These engines typically include several cooperative sections that contribute in some way to the energy conversion process. In gas turbine engines, air discharged from a compressor section and fuel introduced from a fuel supply are mixed together and burned in a combustion section. The products of combustion are harnessed and directed through a turbine section, where they expand and turn a central rotor shaft. The rotor shaft may, in turn, be linked to devices such as an electric generator to produce electricity.
To increase efficiency, engines are typically operated near the limits of the engine components. For example, to maximize the amount of energy available for conversion into electricity, the products of combustion (also referred to as the working gas or working fluid) often exit the combustion section at high temperature. This elevated temperature generates a large amount of potential energy, but also places a great deal of stress on the downstream fluid guide components, such as the blades and vanes of the turbine section. In an effort to help these components withstand this temperature these blades and vanes are often cooled.
In fluid guide components with an internal impingement and external surface (leading edge showerhead and side film) cooling design, a basic concern is the maintenance sufficient backflow margin. This means ensuring that the pressure supplying the showerhead surface holes is maintained above the external static pressure in the leading edge region during all operating ranges. This backflow requirement must be met while simultaneously ensuring that the fluid guide component side walls are also sufficiently cooled. Traditionally, a perforated impingement tube or insert in conjunction with dams or other sealing partitions or is used to accomplish this. The dams help isolate the leading edge cooling region and associated cooling holes from influences which might jeopardize the backflow margin, including manufacturing imperfections or assembly misalignment within the side wall cooling regions, fluctuations in external static pressure, and variation induced by permitted manufacturing tolerances, including cooling hole size and location. This isolation is beneficial because the cooling holes in the leading edge and side regions are typically fed from the same cooling cavity. The dams also create flow-wise separated regions so that the desired impingement pressure ratios can be generated to provide the necessary internal cooling along the fluid guide component sidewalls. The dams also provide a means of positioning the insert. Accordingly, sealing dams provide performance and assembly benefits, in some cases. Unfortunately, sealing dams often do not perform as expected.
In practice, manufacturing tolerances often result in the dams being incorrectly positioned or improperly sized. Also, impingement inserts are often installed during a so-called xe2x80x9cblindxe2x80x9d assembly, which is difficult to observe directly. As a result, it is difficult to ensure that the impingement inserts are correctly positioned. If an impingement tube is installed or manufactured incorrectly, associated impingement holes may be blocked or leakage around the sealing dams may occur. Misalignment or other incorrect insert assembly can significantly reduce the available impingement cooling, with the further result of jeopardizing the backflow margin of the leading edge cooling region. Failures of this type may result in reduced life of the fluid guide component or even complete failure of the component.
Therefore, there remains a need in this art for a fluid guide component that meets cooling requirements while remaining insensitive to the presence of sealing dams or positioning members and minimizing the necessary cooling flow requirements for a given engine performance. The component should include hollow portions or cavities having impingement hole arrays sized so that substantially-uniform pressure is obtained on the downstream side of the impingement insert on all sides of associated positioning members or sealing dams. This pressure obtained within each cavity should meet the minimum back flow requirements for the highest external pressure encountered by the given cavity. The component should also address possible losses in impingement cooling effectiveness, as well as issues related to overflowing of the external cooling holes.
The present invention is a flow guide component having improved tolerance to assembly and manufacturing variations. The guide component includes features that reduce or eliminate sensitivity to the presence of the insert seals, dams, or positioning members, while minimizing the necessary cooling flow requirements for a given engine performance.
Accordingly, it is an object of the present invention to provide a fluid guide component for a combustion engine that ensures substantially-uniform pressure is obtained on the downstream side of an impingement insert on all sides of the associated positioning members or sealing dams.
It is a further object of the present invention to provide a fluid guide component for a combustion engine that address possible losses in impingement cooling effectiveness.
It is an additional object of the present invention to provide a fluid guide component for a combustion engine that addresses possible overflowing of the external cooling holes.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.